Process for the recovery of sulphur from its combinations with hydrogen or oxygen



Patented Sept. 1, 1936 l UNITED sTATEs PEooEss Fon THE RECOVERY OF sm.-

PHUE- FROM rrs companions wrrn nYDnoGEN on OXYGEN Wallace J. Murray, Beading, Mass., assignor to Arthur D. Little, Incorporated. Cambridge, Mass., a corporation of Massachusetts Application June 21, 1932, serial No. 619,426

24 Claims. This invention relates to the art of treating I hydrogen sulphide and/or sulphur dioxide, wheth' er occurring in gaseous or liquid mixtures, andmore particularly to a method for the separation of these gaseous sulphur compounds from industrial or waste gases in which their presence creates an industrial nuisance or lowers the utility value of the gases with which they are admixed.

The desirabilityof accomplishing the result to vwhich my process is directed is apparent and well recognized in such industries as the refining of petroleum, the manufacture of industrial heating gases, the distribution of natural gas, and for the economical recovery and prevention of dispersion of obnoxious sulphur compounds in various branches of the .chemical industry. While the process is herein described with speciiic refer- A ence to the disposal of hydrogen sulphide from petroleum refinery gases Iand distillates, it willv be understood that no limitation 'is thereby intended or implied. On the contrary, the process "is of very general'utility and its application to a `variety of uses will hereafter be indicated.

Among the salient objects of this invention are to mentioned: (l) to provide an efcient and practical process for handling a Wide variety ofvgases in which hydrogen sulphide occurs in low or high percentage, which shall involve the use of simple apparatus only; (2) to provide an economical process in the sense of avoiding the use of expensive chemicals; (3) to provide for the cyclic regeneration of the chemical agents made l use of (4) to avoid the use of sensitive or expensive catalysts; (5) to provide for the recovery of sulphur as a valuable by-product and in a preferred form, A particular object of this invention (to accomplish which its application will be described in detail) is to eliminate the industrial 'nuisance now associated with the refining of certain crude petroleums containing a relatively high percentage of sulphur, of'which the crude petroleum of Crane County, west Texas, is an example.

Qitthe end result of `which accomplishes the result The hydrogen sulphide content of the renery gas iluctuates sharply over widelimits, with the result that a close balance between contents of hydrogen sulphide and 'sulphur dioxide can not practically be attained. It is therefore impractical directly to apply the well known reaction:

(1) 2H2S-i-SO2=`2H2O-l-3S which has'heretofore been proposed as of utility for rthe immediate amelioration of sulphur gas nuisances and the recovery of sulphur. So far as I am aware, practical success in these objects vby use of the reaction of Equation (l) above has not heretofore been attained. The present invention accomplishes in substance the promotion of --this reaction through simple` ancillary reactions,

which would be eiected by the direct reaction of hydrogen sulphide and sulphur dioxide (if such reaction could be practically carried out) to produce water and sulphur.

In petroleum gases the H2B content and the rate of gas evolution are very variable and this makes `it impossible to maintain the ratio of 2H2Sz102, and, therefore, this familiar process can not be used satisfactorily. A

The chemical reactions preferred to be relied upon for the purpose ofthe invention are susceptible of general statement. Depending upon whether hyrogen sulphide, in the general case, or sulphur dioxide is `to be disposed of as in excess in the materials to be treated, the recommended treatment providesA for the generation oi one or the other of these sulphur compounds in such proportion as to satisfy the Equation (l) above. It is, however, unnecessary to maintain this balance at all times, as would be the case if sulphur dioxide and hydrogen sulphide occurring in that mixture were caused to react directly. The process now to be described is cyclic, in the sense that the chemical reagentsused in one step are subinary reaction of the same upon an acidsulphite of an alkaline earth metal such as calcium bisulphite, or a mixture of calcium sulphlte. bisul- 'phite and sulphurous acid, which results in the formation of the thiosulphate. This is readily andV completely soluble in water, especially so long as the solution is kept cool and is not subjected to heating or concentration. In the presence of sulphur dioxide or sulphurous acid the thiosulphate reacts to produce polythionates,

especially when cold and dilute. Upon subjecting the solution, per se, to increased concentration, however, or to heating, or both, the soluble thiosulphate is decomposed to `free sulphur and normal calcium sulphite more completely than by acidification. The calcium sulphite may then be partially or completely dissolved in sulphurous acid to form the acid sulphite or bisulphite and used overagaimA Alkali metal sulphites, on the contrary, form thiosulphates which are not decomposable in this manner and hence are not ap'- plicahlefor the purpose. The recommended v' practice, therefore, includes in order reactions ac- 'ing to Equation (1) cording to the following equations:

Equation (3) represents the known reaction between calcium bisulphit'e (Ca(HSOI:)z) solution and hydrogensulphide (HzS) to form calcium thiosulphate (CaSzOs) which is quite soluble in water, and elementary sulphur as a precipitate. So far as I am aware, Equation (4) represents a reaction lwhich has not heretofore been utilized in a technical process although well known as a chemical reaction. Through the mechanism of this reaction thereis obtainedi` a regeneration of the reagent, rst to normal calcium sulphite and then, by reaction with sulphurous acid or water and sulphur dioxide (according to Equation (5)) to calcium bisulphite. which may again be made use of' in the reaction of Equation (3). Reactions (3) and (5) should take place at relatively low temperatures to pre- 'vent the decomposition of Ca(HSOa)a and to inv crease the solubility of the gases HzS and SO2.

Reaction (4) is favored by high temperatures as CaSzOa is moderately stable at low temperatures. The summation of reaction according to Equations (3), (4), and (5) gives a reaction accordupon the elimination o f the reagent substances recovered by reaction according to (5) as -Ca(HSO;-s) n, which is thereupon re` turned to reaction (3). It follows that practice of reactions (3), (4) and (5) in order produces the results of reaction according to Equation (1) with the advantage of eiiecting reaction with .the HaS and the SO2 severally. This provides for quantitativeadjustment in said stages severally.

In practice, the simple balancing of Equations (3), (4) and (5) may not be fully realized when the balance oftwo HcS to one SO;l is maintained, owing to certain side reactions which will either precipitate calcium in the form of an insoluble compound or yield other salts of sulphur acids which -should be cyclic system.. For example, under certain conditions, such as acidiiication or reaction with sulphur dioxide before decomposing the thiosulphate there will be formed polythionates. which will not react similar to simple calcium thiosulphate made use of in Equations (4) and (5). But the thiosulphate solution may besubstantlally completely decomposed by heat or concentration to form caso: and s according to reaction 4).

, hydroxide or The thiosulphate may be similarly decomposed by acidication and heating or concentrating. To such extent as reactions to polythionates may occur, with consequent loss of reagents, itwill thiosulphate by performing the following reactions, which start with calcium milk of lime, and utilizing their products: y (6) 'CamH):+2HaS=Ca(SH):+2Hz0 The sulphur dioxide required by Equations (l). (5) and (7) may be produced by burning part of the gaseous hydrogen sulphide. as:

(s) 2ms+sol=2mo+2soi cr by. burning part nr the sulphur prduceu in the process as: l

f-aosasoa periodically purged from theV 4with calcium. bisulphite solution to s'uiphite scrubber-s. Calcium 'but its use for this purpose is Equation (6) represents the reaction between calcium hydroxide (Ca(0H) z) and hydrogen sulphide to form calcium hydrosulphlde (Ca(SH)z):

Equation (7), the reaction between calcium hy` drosulphide and sulphur dioxide to form calcium thiosulphate, sulphur and water. In practice, if necessary. the replenishing of the reagents when depleted by side reactions or losses of other originl can be secured by making and -substituting fresh batches in this simple and feasible way. These latter reactions are not, however, of basic importance in my process, and I recognize that their function may be served in other ways. Any reaction capable of yielding either calcium blsulphite or calcium thiosulphate canand may be employed in place ofl these suggested.

Having considered the general chemical aspects of this process and-'presented the specic reactions therein made'use oi',.an application to a particular industrial problem, that of handling the large quantities of sulphurous gases as evolved in the rening of high sulphur crude petroleum will now be described in detail. The particular method now to'be described is in itself another aspect of my present inventio l In the distillation of such crude petroleums as those from Crane County, Texas, the hydrogen sulphide problem presents itselfl in three phases. 'I'he ilrst phase is in the liquid run down from the still, which is saturated with hydrogen sulphide. This is recommended to be taken from the bottom of a gas separator, and caused to ow upward through an appropriate scrubber filled with milk of lime. 'I'his removes the hydrogen sulphide as calcium hydrosulphide, which is used in a later step in the process; for example. a reaction according to Equation (6).

In the second phase hydrogen sulphide comes oif inv gases of high concentrations during a brief period of the batch distillation. In the case of continuous operation, gas highly inclusive of Has will come oi! in an intermediate ilash tower at about 400 F. This gas may be burned in an open llame, or if it'is desired to s ave the hydrocarbons present, it may be mixed with air and burned in contact with iron oxide or other catalyst in a closed kiln. In' this case the hydrogen Ysulphide will be preferentially burned, leaving the hydrocarbos unchanged. I'he to Equation (5) or (7) ing the later part" of the distillation process is handled. The hydrogen sulphide concentration during this phase burning to sulphur dioxide, but it may scrubbed either with milk of lime hydrosulphide (according to Equation (6)), or give calcium thiosulphate (according to Equation (3)). It is evident that the lime and bisulphite should be allowed to react in separate scrubbers, since lime and bisulphite react to give insoluble normal calcium sulphite. A recommended practice is to the end of the system` to react and combine lwith any hydrogen sulphide not Iabsorbed by the bibisulphite maybe of the first phase, not recommended since this would leave free sulphur in the oil. For a few special uses thepresence of free sulphur in the oil is'desirable,

usedfor scrubbing -the liquids is too low to permit eiilcient t andintheseusestheprovision of bisulphite for liquid washing will be satisfactory.

A'iinal step in the process is recommended to comprise scrubbing the sulphur dioxide out of the gases of combustion of thesecondphase by passage through scrubbers containing a solution ofV calcium sulphite (reaction of equation (5)) followed by passage through scrubbers containing calcium hydrosulphide (reaction of Equation (7) of which the latter compound is the better absorbent for sulphur dioxide. Since the first reaction of sulphur dioxide on calcium hydrosulphide is to produce calcium thiosulphate, it is evident that a mixture of calcium hydrosulphide and calcium thiosulphate may be used in the scrubbers if desired.

The action of sulphur dioxide on calcium hydrosulphide produces free sulphur as well as calcium thiosulphate. The calcium thiosulphate thus obtained is soluble in water, per se, but upon acidification or concentrating or heating, decomposes to calcium sulphite and sulphur in accordance with Equation (4). It is significant that such solubility has not heretofore been fully recognized and, in fact, some of the more recently published solubility factors for this compound relate to warm or acidified solutions and give low solubilities, although the data of Kruman and Rodermund in Zeit. fr Anorg. Chem. 86 373 (1914) show (and these dataI have been confirmed by experiment) that at 9 C. 29.34 parts by weight of CaS2O3 dissolve in '70.66 parts by weight of water, or approximately equal parts of the hydrated salt and of water. Such concentrated solutionsor even more dilute solutions upon warming;- 'tend to decompose according to Equation (4) so that if the solutions are subsequently tested, they will show a very low solubility for the residual thiosulphate. On the other hand, if such solutions are treated with sulphur dioxide, and especially when cold and dilute, the thiosulphate is in large part converted to polythionates which are undesirable for the purposes of this invention, and may decompose still further into calcium sulphate. But if the thiosulphate solution is heated or concentrated, or both, the thiosulphate is decomposed to calcium sulphite and free sulphur, which are insoluble. It is not practicable, therefore, to filter the mixture. Upon treating with sulphur dioxide, the calcium sulphite is converted. to bisulphite which is partly soluble.-

though some sulphite tends to remain undissolved.

It has been found, however, that sulphur may be readily and completely separated by filtration of the thiosulphate solution.

It is a further observation that if the thiosulphate be inadvertently transformed to polythionates, these may be converted back to the thiosulphate or to sulphite as follows:

- actas absorbing reservoirs in balancing the hydrogen sulphide and sulphur dioxide'produced at variable rates and at different times during their conversion according to Equation (1) to water and elemental sulphur. Compounds of the alkali metals may not take the place of lime in this process since their thiosulphates do not decompose readily to sulphites which may react with sulphur dioxide to form bisulphites but slowly the process.

react to give trithionates or polythionates, which are useless in this process, but compounds of other alkaline earth metals, for example, magnesium, are operative. While sodium hydroxide, for an instance of use of an alkali metal compound, can not fully take the place of lime, this substance may be used to eflect a slightly more thorough scrubbing of the liquids, and therefore a final soda lye scrub after the lime scrub may be desirably employed in some cases.

The small quantity of lime lost by side reactions may be made up by additions to the lime scrubber.

One form of apparatus and recommendation for practical carrying out of my process for the disposal of sulphur compounds occurring in petroleum will now be described with the aid of the accompanying drawing, in which the gure is a diagram and flow sheet, and in which:

A still and furnace A of any suitable type for vaporizing the oil is provided with a vapor line I to conduct vapors through a condenser B of any suitable type to a gas separator C from the bottom of which the liquid products are. caused to fiow through a line 2, and from the top of which the uncondensed gases flow through a line 2a. Line 2 delivers to a scrubber D containing milk of lime through whichthe liquids are passed upwardly by gravity, andI from which the liquid overflow through valved line 3 may pass to the bottom of a scrubber E containing a solution of sodium hydroxide, NaOH, through which the liquids freed from hydrogen sulphide pass upwardly to line 4 and to a receiver, not shown. Vapor or gas flow through line 21 may be initially to scrubber F containing a solution of calcium bisulphite, through which the gases pass upwardly and through line 5 to another scrubber G containing milk of lime to receive and scrub the gases leaving scrubber F; the purified gaseous hydrocarbons free from hydrogen -sulphide which may be utilized for heating or otherwise, flow off through line 6. Since the desiredv reaction in tank F corresponds to that indicated by Equation (3), and since it is desirable to promote therein a relatively high concentration of calcium thiosulphate, without reaction to the polythionates, it is desirable to provide a low temperature thereof, as by circulating a cooling medium through the outer jacket F.

After a period of operation, the scrubber F contains liquor of calcium thiosulphate, CaSzOa, and finely divided sulphur in suspension; from time to time or continuously this liquor may be drawn off through line 'l and pump 8 to a filter press H for filtering the sulphur out of the thiosulphate liquor. The sulphur is withdrawn as shown and the filtered thiosulphate solution may be delivered to a sulphur dioxide scrubber L through line 9. Scrubber L may be thus supplied with calcium thiosulphate or may contain a mixture of calcium thiosulphate and calcium hydrosulphide, which products are formed -at different stages in Scrubber L may also be provided with a jacket L for circulating a suitable heating medium, such as hot water or steam, to promote the progress of decomposition of the thiosulphate solution to sulphite and free sulphur, preferably in advance of the introduction of sulphur dioxide. The sulphur dioxide for such addition may be provided by a sulphur burner J with air inlet I3, the effluent sulphur dioxide being conducted to the chamber L through pipe l5.

Gases from separator C may flow through a valved line I2 joining line 2^u to a closed kiln K containing ferrie oxide' or other catalyst, for

the selective combustion of hydrogen sulphide, the hydrocarbon and resultant SO2 product ilowing through line I1 to the bottom of scrubber L. The rate of production and quantity of SO2 gas produced and acted upon in scrubber L is, of course, readily controllable. Since it is found that reaction according to Equation (5) is promoted by using relatively high concentrations of sulphur dioxide gas, such operations are preferably conducted when the concentration of hydrogen sulphide (or other sulphur components in the gases from separator C) is relatively great. OtherwiseI concentrated sulphur dioxide from the burner J is to be preferred. Liquor from scrubber L may be drawn oi by pump 28 through pipe 29. The gasous ow past scrubber L through line I8 lmay be sent through branch I9 to the bottom of a scrubber N containing calcium hydrosulphide, Ca(SH)2, supplied from absorption tank D through lines 25-26. The valved pipe 241 from scrubber N may lead to a lter press P for recovering'sulphur from the educt reagent liquid from scrubber N which is essentially CaSzOs. Valved pipe IIJ conducts this solution from lter press P to scrubber L where it is converted to bisulphite. Heat resulting from burning at J or at K may be utilized to dry the sulphur product, or otherwise, as' desired.

In case of the A:formation of polythionates, through inaccuracies of operation or accumulation in the reagent cycle-they may be regenerated in accordance with reaction of- Equation (.10) or (11) by the introduction of hydrogen sulphide gas into tank L or F (under conditions of high concentration of H2S), or by introduction of calcium hydrosulphide solution thereto from line 25 by opening valve 21.' The latter is preferable since the reaction is reversible and alkalinity favors thiosulphate formation.

A` preferred operation is as follows:

'I'he oil is vaporized in still A and the vapors formed thereby are conducted through vapor line I to condenser B, whereby the condensable constituents of the gas are liqueed. From the condenser B the liquid and uncondensed vapors are conducted through line I to the gas separator C.

From the bottom of the gas separator C the liquids ilow into the lower part of scrubber D, which contains milk of lime, which removes the hydrogen sulphide which is contained as an impurity in the distillates from the oil. The resulting product from the reaction of hydrogen sulphide and lime is calcium hydrosulphide. This reaction product is caused to flow from scrubber D through line 25 and branch 21 into scrubber L or through branch 26 into scrubber N. The liquids which have been scrubbed in scrubber D may be caused to ilow through line 4 to the receiver house. If, however, all of the hydrogen sulphide has not been removed from the liquids in. scrubber D, the liquids may be caused to flow through valved branch 3 into the lower part of scrubber E which contains a solution of sodium hydroxide and out at the top through line 4 to the receiver house. Suitable valves controlling the connecting lines may be provided as indicated in the diagram. More than one scrubber may be provided either for milk of lime or for sodium hydroxide within this invention.

During the early stages of treatment 0f a batch instill A, the uncondensed vapors contain a large amount of hydrogen sulphide, and these are recommended to be caused to iiow from the top of `separator C through line I2, through kiln K, containing ferric oxide or other suitable catalyst,

and supplied with sumcient air through passage I 4 so that the hydrogen sulphide will be preferentially oxidized and the hydrocarbons saved. In this case also the resulting gases, consisting of sulphur dioxide and hydrocarbons, are passed through line I1 into scrubber L. In either case, this stage of treatment results in utilizing the sulphur of the still gases to make calcium bisulphite in scrubber L, as well as free sulphur, to be recovered for by-product value.

In the later stages of treatment of a batch in still A, the vapors from gas separator C contain a greater proportion of hydrocarbons and a smaller proportion of hydrogen sulphide, and jin this stage it is recommended that the gases be not burned; the gases are instead caused to iow through line 2 either through scrubber F, containing calcium bisulphite, and then through scrubber G, containing milk of lime; or only through scrubber F; or only through scrubber G. If only scrubber F is used, line 5 is closed. If both scrubbers F and G are used, line 5 is open and lines E and 2fi closed between s crubbers F and G. If only scrubber G is used, lines 5 and 6 between Fand G are both closed. In any of these cases, the scrubbed hydrocarbons are caused to flow through the exit line 6 to theA boiler house, lthe atmosphere or to the gasoline recovery plant; they yare substantially free of hydrogen sulphide.

The calcium bisulphiteutilized in scrubber F is formed during the process in scrubber L, as above mentioned. 'Ihe action of hydrogen sulphide on calcium bisulphite causes the formation of calcium thiosulphate and sulphur. The liquid containing these two products is caused to ilow from scrubber F through line 1 to lter press H in which the sulphur is separated and is removed, and the calcium thiosulphate liquor may be caused to ow through line 9 to scrubber L.

In Ascrubber G the hydrogen sulphide and lime form calcium hydrosulphide, and this materialV may be caused to ow from scrubber G through lines 21 and 26 into scrubber N. The calcium thiosulphate for this scrubber or series of scrubbers is supplied from lter press H through line 9 as described above. .'I'he calcium hydrosulphide is supplied from scrubber D through .line 25, and also from scrubber G through line 21.

The thiosulphate solution in scrubber L preferably is heated, by circulating hot water or steam through the jacket L', whereupon decomposition -to normal calcium sulphite and free sulphur takes place. It is then treated with concentrated sulphur dioxide gas to convert the sulphite vto more soluble form of bisulphite. 'Ihe reaction need not be eiiective to convert all -of the sulphite t bisulphite, since this will be promoted upon recycling to absorber F. It is, however, desirable to saturate the same thoroughly with sulphur dioxide gas, an appreciable proportion of which will dissolve as sulphurous acid without immediate reaction with the calcium sulphite. When the gas containing sulphur dioxide produced in kiln K is passed into scrubber L as described above, L. the mixture is purified and residual hydrocarbons may flow through line I8 to the atmosphere; or if they contain suiiicient hydrocarbons for fuel, they may be delivered to the boiler house or any after passing through scrubber 6,;

other place' requiring fuel. The liquid containing 70 calcium bisulphite, calcium sulphite, and sulphur may be caused to ow from scrubber L through line 29, pump 28 and line 23 into scrubber F.

In the second procedure, calcium thiosulphate and calcium hydrosulphide are run into and reacted upon in separate scrubbers L and N, respectively, the calcium thiosulphate in scrubber L and the calcium hydrosulphide in scrubber N. 'I'he gases containing sulphur dioxide are then passed through scrubber L and thence through line I9 into scrubber N and out through line I8 to the atmosphere or boiler house.

Since the calcium thiosulphate has previously been decomposed to Icalcium sulphite and free sulphur, the sulphur dioxide. reacts with calcium sulphite in scrubber L to form calcium bisulphite. These products (calcium sulphite, calcium bisulphite and free sulphur) are now caused to iiow back to scrubber F through lines 29 and 23, as above described. The residual gas (or original gas stream) then passes to scrubber N. The products formed yin scrubber N are calcium thiosulphate and sulphur, and are caused to flow from scrubber N through line 24 to filter press P in which the sulphur is separated and removed. The calcium thiosulphate liquor may be caused to iiow from filter press P through line Il) into scrubber L.

The drawing is a diagram only, and it will be understood that the apparatus may include at any point storage or relief tanks for gases or liquids circulated or utilized in the treatment described; that continuous as well as batch treatment of the materials to be deprived of their detrimental sulphur inclusions may be restortcd to without substantial change except the provision of alternatively used vessels for the several stages of treatment, not shown. While the process hasV been described in connection with apparatus, it is apparent that apparatus capable of practicing the process may be provided by conventional design withinl the knowledge of those skilled in the art and informed by the disclosure of this specification. While the process has been described for a specific instance as carried out upon distillation products from heavily sulphuretted petroleum, the invention is applicable without change to the conversion. and elimination of sulphurbearing components of products of many other industrial eiorts; for example, the smokes andfumes of metallurgical operations, coke ovens and other distillations.

This application is a continuation in part of copending application Serial No. 334,778, rlled January 24, 1929.

I claim:

l. Process of treating gases containing hydrogenl sulphide to remove sulphur compounds which comprises the steps, scrubbing the gases with a solution containing an alkaline earth metal bisulphite to form the corresponding thiosulphate and precipitated sulphur, and thereafter converting the thiosulphate so found to`sulphur and sulphite, treating the latter to regenerate the bisulphite, and treating more gas with said bisulphite. 4

.2. Process of treating gases containing hydrogen sulphide, which comprises scrubbing a part of such gases with a solution of an alkaline earth metal bisulphite, to form thiosulphate and precipitated sulphur, converting the hydrogen sulphide in' another part of the gas to sulphur dioxide, subjecting the thiosulphate to decomposition to the corresponding sulphite and sulphur and thereafter treating the reaction mixture with said sulphur dioxide.

3. Process of treating gases containing hydrogen sulphide, which comprises scrubbing a part of such gases with a solution of an alkaline earth metal bisulphite, to form thiosulphate and precipitate sulphur, converting the hydrogen sulphide in another part of the gas to sulphur dioxide, subjecting the thiosulphate to decomposition by heat to the corresponding sulphite and sulphur and thereafter treating the reaction mixture with said sulphur dioxide.

4. Process of treating gases containing hydrogen sulphide, which comprises scrubbing a part of such gases with a solution of an alkaline earth metal bisulphite, to form thiosulphate and to precipitate sulphur, converting the hydrogen sulphide in another part of the gas to sulphur dioxide, subjecting the thiosulphate to decomposition by concentration to the corresponding sul- -phite and sulphur, and thereaftertreating the reaction mixture with said sulphur dioxide.

5. Process of treating gases containing hydrogen sulphide, which 'comprises the steps, scrubbing the gases with a solution containing an alkaline earth metal bisulphite to form the corresponding thiosulphate, and precipitate sulphur, removing the sulphur and decomposing the thiosulphate solution so formed with heat to the corresponding sulphite and sulphur and then treating with sulphur dioxide to regenerate the bisulphite.

6. Process of treating gases containing hydrogen sulphide, which comprises the steps, scrubbing the gases with a solution containing calcium `bisulphite to form calcium thiosulphate, and precipitate sulphur, removing the sulphur and decomposing the thiosulphate solution so formed with heat to the corresponding sulphite and sulphur and then treating with sulphur dioxide to regenerate the bisulphite.

7. Process of removing the sulphur content from gases containing hydrogen sulphide, which comprises scrubbing a part of said gases With a solution of calcium bisulphite, to form calcium thiosulphate and sulphur, removing the latter, decomposing the thiosulphate to sulphite and free sulphur, converting the sulphur components in a part of said gases to sulphur dioxide and reacting upon the sulphite with said sulphur doxide to form bisulphite.

8. Process of removing the sulphur content from gases containing hydrogen sulphide comprising scrubbing the gases with a solution of calcium bisulphite to form calcium thiosulphate and free sulphur, removing the latter, decomposing the thiosulphate to sulphite and sulphur, converting the sulphur components in a part of said gases to sulphur dioxide, reacting upon the sulphite with said sulphur dioxide to form bisulphite and returning the liquid product to the scrubbing operation.

9. Process of removing the sulphur content from gaseous admixture containing hydrogen sulphide, comprising as steps severally causing sulphur dioxide to react with an alkaline earth metal sulphite to form bisulphite, and hydrogen sulphide to react with the bisulphite of an alkaline earth metal to form thiosulphate, and decomposing the thiosulphate to sulphite, and subjecting the bisulphite and sulphite products respectively to the action of .the gaseous admixture and' to the action of sulphur dioxide to regenerate the said thiosulphate and bisulphite respectively.

10. Process of removing the sulphur content from gaseous admixture containing hydrogen sulphide, comprising as steps severally causing sulphur dioxide to react with calcium sulphite to form bisulphite, and hydrogen sulphide to react with calcium bisulphite to form thiosulphate, and decomposing the thiosulphate to'sulphite, and

. sulphur dioxide in calcium subjecting the bisulphite and sulphite repectively in aqueous solution or suspension to the action of the gaseous admixture and to the action ofsulphur dioxide to regenerate the said thiosulphate and bisulphite respectively.

11. In a process for removing hydrogen sulphide from vapors and gases, the step of promoting an eventual reaction between the hydrogen sulphide and sulphur dioxide through their stage interaction with .an alkaline earth metal bisulphite and an alkaline earth metal sulphite, respectively, in aqueous solution or suspension, the

reaction in eachregnerating material for the so-v lution in the other, with intermediate decomposition of thiosulphate generated by the action of the hydrogen sulphide on the bisulphite and removal of sulphur.

12. The process of recovering sulphur from .petroleum, which consists in distilling the same whereby the bulk of the sulphur present will be evolved as hydrogen sulphide either dissolved in the liquid condensates or present in the still gases, separating the liquid condensate from the gases so liberated, scrubbing lthe distillation products in part with calcium bisulphite liquor, while convertingL the remaining part of the gaseous hydrogen suphide to sulphur dioxide and absorbing the sulphite, thereby to generate further calcium bisulphite.

13. The process of recovering sulphur from*Y petroleum, which consists in distilling the same whereby the bulk of the sulphur present will be evolved as hydrogen sulphide either dissolved in the liquid condensates or present in the still gases, separating the liquid condensate from the gases so liberated, scrubbing the distillation products in part with calcium sulphite and bisulphite while converting the remaining part of the gaseous hyogen sulphide to sulphur dioxide and treating calcium sulphite therewith toV generate further calcium bisulphite. l

14, The process of recovering sulphur from. petroleum, which consists in distilling a crude oil containing sulphur, converting the hydrogen sulphide of the gaseous component from the Vrsty stage of the distillation to sulphur dioxide, and thereafter causing the sulphur dioxide to react with alkaline earth metal lsulphite to formgthe bisulphite which is then reacted with hyrogen sulphide contained in the gaseous eiiiux from the last stage of distillation to form thiosulphate and sulphur.

15. The process of recovering sulphur fromv petroleum, which consists in distilling a crude oil containing more than one percent of sulphur, burning the hydrogen sulphide evolved in the irst stage of the distillation to form sulphur dioxide, and absorbing this sulphur dioxide in a suspension containing calcium sulphite, said sulphite resulting from the reaction of the hydrogen sulphide of the leaner gases of the last stage of the distillation on a solution containing calcium bisulphite, and decomposition of the resulting calcium thiosulphate, thereby to regenerate calcium bisulphite.

16. Process of treating gases containing hydrogen sulphide to remove sulphur compounds, which comprises the steps. scrubbing the gases with a solution containing an alkaline earth metal bisulphite and sulphur dioxide, and adding to the rephite and sulphur dioxide, and adding to the resulting liquor alkaline earth metal hydrosulphide to promote the -formation of the corresponding thiosulphate and sulphur, separating the sulphur, and decomposing the thiosulphate to sulphite and free sulphur.

18. Process of treating-gases containing hydro- I gen sulphide, which comprises the steps, scrubbing the gases with a solution containing an alkaline earth metal bisulphite'to form the corresponding thiosulphate, and precipitate sulphur, removing the sulphur and decomposing the thiosulphate solution so formed by heat and concentration to the corresponding sulphite and sulphur and then treating with sulphur. dioxide to regenerate the bisulphite.

19. Process of "removing the vsulphur content'r from a gaseous admixture containing hydrogen sulphide and sulphur dioxide in which the sulphur dioxide predominates, comprisingl as steps subjecting the gaseous mixture to prolonged inti- -mate contact with an aqueous suspension of alkaline earth `metal sulphite and adding alkalineA earth metal sulphhydrate to said aqueous suspension.

2 0. Process of removing the sulphur content from a'gaseous admixturecontaining hydrogenA sulphide and sulphur dioxide inwhich the hydrogen sulphide predominates, comprising as steps subjecting the gaseous mixture to prolonged intimate contact with an aqueous suspension of alkaline earth metal sulphite and adding sulphur-ous acid to the aqueous suspension.

21. Process of removing the sulphur vcontent from gaseous and liquid products containing yhydrogen sulphide, comprising as steps subjecting the same to contact with alkaline earth metal bisulphite to form alkaline earth metal thiosulphate, decomposing the thiosulphate to sulphite and sulphur and reconverting the sulphite torbisulphiteffor reuse.:L

22. Process of removing the sulphur content from gaseous and liquid products containing hydrogensulphide, comprising as steps subjecting the same to contact with calcium bisulphite to form calcium thiosulphate, decomposing the thiosulphate to sulphite and sulphur, and reconverting the sulphite to bisulphite for reuse.

23. Process of recoveringthe sulphur content from gaseous and liquid products containing sulphur dioxide, comprising as steps converting the sulphur dioxide to alkaline earth metal thiosul WALLACE J. MURRAY. 

